After nearly two decades of rapid development, there was a qualitative leap in material synthesis, device preparation and process integration for Organic Light Emitting Diode (OLED). As OLED has high efficiency, high brightness, high contrast, low power consumption, fast response, flexible display and many other advantages, OLED has become the most powerful competitors for the next generation of mainstream flat panel display technology.
As depicted by FIG. 1, a pixel structure of OLED according to conventional arts comprises a plurality of thin film transistor array circuits 11 on a substrate 10, an anode 12 on the thin film transistor array circuit 11, a pixel definition layer 13 on the anode 12, an organic light emitting layer 14 on the pixel definition layer 13, and a cathode 15 on the light emitting layer 14. The pixel definition layer 13 functions to coat the edge of the anode 12, and define the light emitting area of the OLED. Since a metal oxide such as indium tin oxide (ITO) is generally used as the anode 12 of the OLED, and ITO has a great crystal grain. And at the same time, the edge of the etched ITO is straight, almost at right angles of 90°, and the thickness of the ITO electrode is great, typically 1500 Å to 2000 Å. If there is no pixel definition layer 13, it is easy for the cathode 15 to short-circuit with the anode 12 at a 90° right angle of the edge of the anode 12, such as a short circuit at a position indicated by the dotted line region 16 in the figure.
However, the presence of the pixel definition layer reduces the light emitting area, and in particular, the pixel area is required to be as small as possible in the present trend of high resolution display, and the presence of the pixel definition layer further reduces the light emitting area, such that requirements for efficiency and life expectancy are further raised.